The force exerted by the club on the ball is comparable to the speed of the club head at impact with the ball. The hands, arms and body swing of the club produces the base speed of the club head. It is to be noted that the wrists travel at the same relative speed as the hands and club shaft in this base swing. Thus if the wrists are held straight, they neither add or detract from the base speed of the swing.
However, if the wrists are cocked-back from the target on the backswing and then uncocked on the downswing, the club head not only is traveling at the base speed of the arm swing but has an added increment of speed from the swing of the wrists in their uncocking pivot. Thus it is advantageous to have a wrist swing imposed piggy-back on the base arm swing as this greatly accelerates club head speed at impact with the ball.
It is difficult to teach the super-imposition of the wrist swing on the arm swing together with all the other do's and don'ts of golf instruction. Moreover, while the teacher may put the player's hands and wrists through the proper motions, angles and positions, it is quite different from the player doing it himself because he does not get the action and feel of self-performance which is essential to his understanding.
A player is at a great disadvantage if he does not know how to add the velocity of the swing of his wrists to the velocity of his arm swing.
The generally accepted cocked angle of the wrists is that the club shaft lies at a right angle to the off-target forearm of the player. It is also generally accepted that the wrists are cocked on the backswing when the hands reach the level of the hips. The wrists are held cocked during the remainder of the backswing with the left arm straight. The downswing is then entered with the left arm straight and the wrists held cocked until the hands again reach the level of the hips. Then the wrists are uncocked which adds the velocity of the wrist pivot swing to the pivot swing of the arms. This whips the club head through the ball at the combined speeds of the arm swing and the wrist swing.